From 5c61c0240dc6bae176ef858ee7d5b325797da049 Mon Sep 17 00:00:00 2001
From: "Valeriano A.R" <valen.alfonso@gmail.com>
Date: Wed, 5 Dec 2018 10:20:11 +0100
Subject: [PATCH] Code for Day05 part 1

---
 AdventOfCode2018.Tests/Day05_Tests.cs | 88 +++++++++++++++++++++++++++
 AdventOfCode2018/Day05.cs             | 43 ++++++++++++-
 2 files changed, 129 insertions(+), 2 deletions(-)

diff --git a/AdventOfCode2018.Tests/Day05_Tests.cs b/AdventOfCode2018.Tests/Day05_Tests.cs
index f6f33d5..8063619 100644
--- a/AdventOfCode2018.Tests/Day05_Tests.cs
+++ b/AdventOfCode2018.Tests/Day05_Tests.cs
@@ -14,5 +14,93 @@ namespace AdventOfCode2018.Tests
 
             Assert.AreEqual("10", result);
         }
+
+        #region ReducePolymer
+
+        [TestMethod()]
+        public void ReducePolymer__Remove_cC()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.ReducePolymer("dabAcCaCBA");
+
+            Assert.AreEqual("dabAaCBA", result);
+        }
+
+        [TestMethod()]
+        public void ReducePolymer__Remove_cC_AtEnd()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.ReducePolymer("dabAcC");
+
+            Assert.AreEqual("dabA", result);
+        }
+
+        [TestMethod()]
+        public void ReducePolymer__Remove_Only_cC()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.ReducePolymer("cC");
+
+            Assert.AreEqual("", result);
+        }
+
+        [TestMethod()]
+        public void ReducePolymer__Remove_cC_AtStart()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.ReducePolymer("cCAAAA");
+
+            Assert.AreEqual("AAAA", result);
+        }
+
+        [TestMethod()]
+        public void ReducePolymer__Remove_Aa()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.ReducePolymer("dabAaCBA");
+
+            Assert.AreEqual("dabCBA", result);
+        }
+
+        [TestMethod()]
+        public void ReducePolymer__Remove_cCc()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.ReducePolymer("dabCBAcCcaDA");
+
+            Assert.AreEqual("dabCBAcaDA", result);
+        }
+
+        [TestMethod()]
+        public void ReducePolymer__Irreductible()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.ReducePolymer("dabCBAcaDA");
+
+            Assert.AreEqual("dabCBAcaDA", result);
+        }
+
+        #endregion ReducePolymer
+
+        #region FullyReducePolymer
+
+        [TestMethod()]
+        public void FullyReducePolymer__Test()
+        {
+            Day05 day05 = new Day05();
+
+            string result = day05.FullyReducePolymer("dabAcCaCBAcCcaDA");
+
+            Assert.AreEqual("dabCBAcaDA", result);
+        }
+
+        #endregion FullyReducePolymer
     }
 }
\ No newline at end of file
diff --git a/AdventOfCode2018/Day05.cs b/AdventOfCode2018/Day05.cs
index e14cf3e..5bb354d 100644
--- a/AdventOfCode2018/Day05.cs
+++ b/AdventOfCode2018/Day05.cs
@@ -1,4 +1,6 @@
-namespace AdventOfCode2018
+using System.Text;
+
+namespace AdventOfCode2018
 {
     /*
     --- Day 5: Alchemical Reduction ---
@@ -31,9 +33,46 @@
 
     public class Day05
     {
+        public string ReducePolymer(string polymer)
+        {
+            if (polymer.Length <= 1) { return polymer; }
+            StringBuilder sb = new StringBuilder();
+
+            int i;
+            for (i = 1; i < polymer.Length; i++)
+            {
+                char previousCharacter = polymer[i - 1];
+                char character = polymer[i];
+                if (previousCharacter != character && char.ToLower(previousCharacter) == char.ToLower(character))
+                {
+                    i++;
+                }
+                else
+                {
+                    sb.Append(previousCharacter);
+                }
+            }
+            if (i == polymer.Length) { sb.Append(polymer[i - 1]); }
+
+            return sb.ToString();
+        }
+
+        public string FullyReducePolymer(string input)
+        {
+            string previousPolymer = null;
+            string polymer = input;
+            do
+            {
+                previousPolymer = polymer;
+                polymer = ReducePolymer(polymer);
+            } while (previousPolymer.Length > polymer.Length);
+            return polymer;
+        }
+
         public string ResolvePart1(string input)
         {
-            return null;
+            string reducedPolymer = FullyReducePolymer(input);
+            return reducedPolymer.Length.ToString();
         }
 
         public string ResolvePart2(string input)